4
COAL & PETROLEUM
CHAPTER
CONTENTS
 Fuels
 Classification of Fuels
 Coal
 Destructive Distillation of Coal
 Petroleum
 Refining
FUELS
(a) Coal
(b) Coke
(c) Wood
(d) Charcoal
(e) Animal-dung cakes
(f) Bagasse, Agricultural wastes
 Liquid fuels : Volatile liquids which
produce combustible vapour are called
liquid fuels. Kerosene is the most
commonly used liquid fuel.
Examples : Some common liquid fuels are :
(a) Petrol
(b) Diesel
(c) Kerosene
(d) Alcohol
Petrol, diesel and kerosene are mixtures of
hydrocarbons.
 Gaseous fuels : Combustible gases or
mixtures of combustible gases are called
gaseous fuels.
Examples : Some commonly used gaseous
fuels are :
(a) Natural gas
(b) Liquefield petroleum gas (LPG)
(c) Biogas (or Gobar gas)
(d) Coal gas
(e) Water gas
(f) Producer gas
(g) Hydrogen gas
(h) Compressed Natural (CNG)
Petroleum gas is obtained as a by-product
during the fractional distillation of petroleum.
A combustible substance which on burning
produces a large amount of heat and light is
called a fuel.
Coal, LPG , Petrol , Kerosene , wood etc.
CLASSIFICATION OF FUELS
Fuels are classified on the basis of physical
sttes in which they occur. So fuels are classified
as solid, liquid and gaseous fuels.
Classification of Fuels
Solid fuels
Liquid fuels
Gaseous fuels
 Solid fuels : Combustible substances which
are solid at room temperature are called
solid fuels. Solid fuels contain mainly
carbon both as free and combined carbon.
In rural areas, Firewood, Agricultural
wastes, Animal-dung cakes are the major
source of energy.
Examples : Some solid fuels are :
 Characteristics of an ideal fuel





An ideal fuel should have the following
characteristics :
It should be fairly cheap and easily
available.
It should burn at moderate rate.
It should not produce any poisonous and
irritating fumes during burning.
It should leave no residue (ash) after burning.
It should produce large amount of heat per
unit mass i.e., it should have high calorific
value.
 It should be safe and convenient from the
storage and tranportation point of views.
 Its ignition temperature should be above
room temperature. So that it is safe to use
such a fuel.
 Uses of Fuels
 Cooking and Heating : The most common
use of fuels is for cooking and heating. The
commonly used domestic fuels are wood,
dry cattle dung, coal, charcoal, kerosene (in
rural areas) and coal, kerosene, LPG (in
urban areas).
 For Transportation : Fuels such as petrol,
diesel and CNG are used for running cars,
scooters, buses, trucks and trains. These
automobiles are used for transportation
from one place to another. The fuel used in
aeroplanes is called aviation fuel.
 For Generating Electricity : Fuels such as
coal and natural gas are used for generating
electricity on a commercial scale, in
Thermal power stations. Petrol, diesel and
kerosene are also used for generating
electricity in smaller generators commonly
used at homes and shops, etc.
 In Industry : Fuels such as coal, natural
gas, diesel and furnace oil are used in the
industry for generating steam in boilers.
Steam is required in industry for heating
purposes and also for generating electricity
for their own use in factory. Industry in the
rural areas also uses biomass such as
bagasse—the cellulose material left after
extracting juice from the sugarcane for
running boilers.
 For Launching Space Vehicles : Space
vehicles are launched with the help of
rockets. Rockets use special fuels called
propellants. A propellant is a combination
of a fuel and an oxidizer.
COAL
 Introduction :
Coal is a mineral of dark brown or black colour
formed from the remains of plants buried in the
earth’s crust millions of years ago.
 Composition :
Coal is a very impure form of carbon. It
mainly consists of atoms of carbon, hydrogen
and oxygen. A small amount of sulphur is also
present in it.
 Mining
Coal is mined using two methods–opencast
mining and underground mining. Opencast
mining is used when the deposits of coal are
near the surface of the earth. Underground
mining is used when coal deposits lie deep
inside the earth’s crust.
 Formation
Coal is formed from vegatable matter burried
under the earth. About 300 million years ago,
the earth was covered with dense forests,
marshlands and rivers. The forests grew and
died and fell into the waters of the surrounding
swamps. These plants were covered with tons
of earth over a period of millions of years. Due
to the huge pressure and temperature inside the
earth, this vegetable matter got converted into
coal. For this reason, coal is known as fossil
fuel. It is also a non-renewable source of
energy.
 Types of Coal
Coal comes in four main varieties. The
percentage of carbon in air-dried samples are
as follows.
 Peat : This is a material in the first stage of
coal formation. It contains only 27% carbon
and is considered to be the lowest grade of
coal.
 Lignite : This variety of coal contains 2830% carbon. It has poor heating power. It is
brown in colour but lustrous when dry.
 Bituminous : It is a soft coal containing
78-86% carbon. It gives a large proportion
of gas when heated and burns with a
yellow, luminous flame.
 Anthracite : It is a hard coal and contains
94-98% carbon. It is lustrous. It burns
without smoke and gives much heat and
little ash.
Bituminous coal is by far the most useful as
a fuel, but anthracite is considered to be the
most superior in quality.
 Uses :
 Coal is used as a fuel to convert water into
steam to run thermal power plants for the
generation of electricity. It is also used as a
fuel in homes and factories, and to run
steam engines.
 Coal is used in the preparation of fuel
gases, such as coal gas.
 Coal is used in the preparation of synthetic
oil and synthetic natural gas.
 Coal is also used to obtain natural gas. For
this, finely ground coal is heated with
hydrogen under pressure in the presence of
a suitable catalyst. The complex molecules
present in coal combine with
 The destructive distillation of coal gives
coke, coal tar, coal gas, etc.
 Coal is the source from which a number of
organic compounds such as benzene,
toluene, phenol, aniline, naphthalene and
anthracene are obtained.
 DESTRUCTIVE DISTILLATION OF
COAL
The process of destructive distillation is
carried out be heating coal at a high
temperature (1270 K) in the absence of air.
This process is also called as pyrolysis and
yields lot of valuable products.

Products of destructive distillation of coal
(A) Coke
(B) Coal Tar
(C) Amoniacal liquor
(D) Coal gas
 Coke : Solid residue left after destructive
distillation (high percentage carbon-nearly
98%)
 Uses :
(i) As domestic fuel.
(ii) Acts as a good reducing agent in the
manufacture of steel
(iii)Useful fuel gases like water gas and
producer gases can be made using coke.
  Water gas is a mixture of carbon monoxide
and hydrogen. It is obtained by passing
steam over red-hot coke.
C + H2O  CO + H2
 Coal Tar : Coal tar is a midture of different
carbon compounds. It is a thick, black
liquid. The fractional distillation of coal tar
gives many chemical substances which are
used in the preparation of dyes, explosives,
paints, synthetic fibres, drugs and
pesticides. Some of these chemical
substances are benzene, toluene, phenol and
aniline.
 Ammoniacal Liquor :
The ammonia produced as a result of
destrutive distillation of coal is absorbed in
water. The aqueous solution of ammonia,
i.e., ammonium hydroxide solution, is
called ammoniacal liquor. It is used in the
preparation of fertilizers such as
ammonium sulphate and ammonium
superphosphate.
NH3 + H2O NH4OH
2 NH4OH + H2SO4 (NH4)2SO4 + H2O
Coal Gas : Coal gas is a mixture of
hydrogen, methane and carbon monoxide.
The gases present in coal gas are
combustible, and hence it is an excellent
fuel. It has a high calorific value. It was
used for lighting houses, factories and
streets in Mumbai until 1950. It was also
used for cooking until recently.
PETROLEUM
Petroleum is a naturally occurring oil that
consists chiefly of hydrocarbons with some
other elements, such as sulphur, oxygen and
nitrogen. It is now known that petroleum
contains hydrocarbons of the paraffin series,
with upto 100 or more carbon atom s in the
chain. The unrefined form of petroleum is
called crude oil or rock oil (petra = rock;
oleum = oil).
 Origin of Petroleum :
Petroleum was formed from organisms living
in the sea. The remains of these organisms
were deposited in shallow depressions in the
  Producer gas is a mixture of carbon
monoxide and nitrogen. It is obtained when
air is passed over red-hot coke.
2C + O2 + 4N2  2CO + 4N2
sea bed long, long ago. These were covered by
(iv)Used in metallurgical operations as a
reducer for oxide ores.
years, the organic matter present in the dead
layers of sand and clay which compressed
these remains. Over a period of millions of
organisms underwent a series of processes
before
being
into
There are some government agencies engaged
petroleum. The petroleum migrated from the
in exploring and producing crude oil-Oil and
source
large
Natural Gas Commission (ONGC) and Oil
underground reservoirs beneath impermeable
India Limited (Oil). There are many refineries
rocks. It often floats over a layer of water and
in India. The larger refineries are at Jamnagar,
is held in this position under pressure beneath
Mathura, Bharuch, Digboi, Haldia and Barauni.
rock
finally
to
be
transformed
entrapped
in
a layer of natural gas.
REFINING
 Oil Wells in India :
In India, oil was first struck at Makum in
The
process
of
separating
the
various
Assam in 1867. The oil fields of Assam were
components of petroleum from one another is
the only source of petroleum in our country
known as the refining of petroleum. This is
until about 40 years ago. Some other places in
done by a process called fractional distillation
our country where oil wells have been dug are
whih is based on the fact that the different
components of petroleum have distinctly
 Ankleshwar and Kalol in Gujarat,
different boiling points.
 Offshore areas west of Mumbai, and
 Offshore deltas of the Godavari and Kaveri
rivers.
Petroleum Gas
Below 40ºC–170ºC
(C1 – C4)
Petrol (Gasoline)
40ºC–170ºC
(C5 – C10)
Kerosene oil
170ºC – 250ºC
(C10 – C12)
Diesel oil
250ºC – 350ºC
(C13 – C15)
Fuel oil
300ºC – 400ºC
(C15 – C18)
400ºC
Crude oil
Lubricating oil
> 400ºC (C17 – C20)
Residual oil (Boilling point
greater than 400ºC)
Paraffim wax
> 400ºC (C20 – C30)
Asphalt
> 400ºC (C30 – C50)

 Asphalt : Asphalt is a black and sticky

substance. It is used for making the surface
of roads. It does not burn readily.
 Paraffin Wax : It boils at above 673 K. It
is obtained by the fractionation of residual
 Products of Petroleum Refining
oil. It is used for making candles, vaseline,
grease, polishes, etc.
 Lubricating Oil : It boils at well above 673
K. It is obtained by the fractionation of
residual oil. It is used for lubricating
machinery.
 Fuel Oil : The boiling range of fuel oil is
623 K to 673 K. It is used in industries to
heat boilers and furnaces. It is a better fuel
than coal because it burns completely
leaving behind no ash, whereas coal burns
producing a large amount of ash which has
to be removed regularly.
 Diesel Oil : Its boiling range is 573 K to
623 K. It contains straight-chain alkanes
with the number of carbon atoms varying
from 20 to 25. It is used in cars, trucks,
buses, and locomotives.
 Kerosene : Its boiling ranges is 443 K to
523 K. It contains straight-chain alkanes
with 10-16 carbon atoms. It is used for
domestic purposes, for lighting petromax,
lanterns, lamps, stoves, etc.
 Petrol : Its boiling range is 313 K to 443 K.
It is also called gasoline. it contains
paraffins from pentane to dodecane. It is
used as a fuel in two-wheelers, threewheelers and cars.
 Residual Oil : The residual oil obtained
from the primary distillation of petroleum is
known as reduced crude. Reduced crude is
distilled in vacuum to yield bitumen as
residue. Bitumen is largely used in making
road surfaces, and also for coating cables to
provide electrical insulation.
 Uses
 Petroleum gas is used as a fuel. It is also
used in the form of liquefied petroleum gas
(LPG) for domestic purposes.
 Gasoline or petrol is used as a fuel in cars,
scooters, etc.
 Kerosene is used as a household fuel.
 Diesel oil is used as a furnace fuel and fuel
for diesel engines.
 Lubricating oil is used for lubrication of
machinery, etc.
 Vaseline is used for softening skin.
 Paraffin wax is used for making candles
 Most industrial chemicals are produced
from petroleum and natural gas. These
chemicals are called petrochemicals.
Petroleum is the major source of medicines,
insecticides, rubbers, plastics, perfumes,
explosives, motor fuels, etc.

Petroleum Gas : It is a mixture of
ethane, propane and butane. Its main
constituent is butane which burns giving off
a lot of heat. Butane is easily liquefied
under high pressure. In the liquid form it is
supplied in cylinders and is commonly
known as Liquefied Petroleum Gas (LPG).
 
Liquefied Petroleum Gas (LPG) :
Liquefied petroleum gas is petroleum gas in
liquid state. It is a mixture of ethane,
propane
and
butane,
but
the
major
component is butane.
LPG is a colourless, odourless (when pure)
gas. The commercially supplied LPG
contains a strong smelling compound called
ethyl mercaptane (C2H5SH) to permit its
detection in the case of any leakage.
EXERCISE # 1
Q.9
What is meant by refining of petroleum ?
Q.10
Where is petroleum found in India ?
Q.11
Name the petroleum product used for
surfacing of roads.
Name the fraction of petroleum used for
making ointments and candles.
Q.12
Expand CNG.
Q.3
How is coke obtained
Q.13
Q.4
Name the purest form of carbon.
Name two fuels which are used for running
automobiles.
Q.5
How is coal tar formed ?
Q.14
Why is food regarded as a fuel for our
body?
Q.6
Give the main use of coal gas.
Q.15
Name a liquid fuel which is used in homes?
Q.7
How is petroleum formed ?
Q.16
Write the full forms of (a) CNG (b) LPG
Q.8
Why is petroleum called a fossil fuel ?
 VERY SHORT ANSWER TYPE QUESTIONS

Q.1
Q.2
Name any two products of petroleum
refining.
EXERCISE # 2
 SHORT ANSWER TYPE QUESTIONS
Q.8
Q.1
Why are coal and petroleum known as
fossil fuels ?
Q.9
Q.2
Give two characteristics of coal.
Q.3
Give two use of coke.
Q.4
Why should the fossil fuels be used with
care ?
Q.5
(a) Name two places in India where oil
wells are found ?
(b) From which natural substance are liquid
fuels formed ?
(b) When and where in India where oil
wells first found ?
(c) Which gas is the main constituent of
LPG ?
(a) Name the products obtained when coal
is heated in the absence of air.
(d) How was petroleum formed in nature ?
(b) Write any two uses of its products.
(e) Why do green leaves not catch fire
easily?
Q.6
Q.7
How is 'petrol' related to 'petroleum' ?
Name four most important products
obtained from petroleium.
Name three products of distillation of
petroleum of petroleum and give their uses.
Give reasons –
(i) LPG is a better domestic fuel than wood.
(ii) Water is not used to control fires
involving electrical equipment.
 LONG ANSWER TYPE QUESTIONS
Q.10
Q.11
(a) What is CNG ? Give its one use.
How is coal formed ?
ANSWER KEY
EXERCISE # 1
Sol.1
Kerosene and Petrol
Sol.2
Bintumen
Sol.3
Coke is obtained by heating coal in the
absence of air.
Sol.4
Coke.
Sol.5
When destructive distillation of coal is
done, the vapours which condense in the
water form coal tar.
Sol.6
Coal gas is mainly used as a fuel in the
coal processing plants.
Sol.7
Petroleum is formed by the decomposition
of dead aquatic plants and animals.
Sol.8
Petroleum is called a fossil fuel as it is
obtained from the bodies of dead
organisms.
Sol.9
The separation of different fractions of
petroleum on the basis of their different
boiling points is known as refining of
petroleum.
Sol.10 In india, petroleum is found in Assam,
Gujrat, Bombay High and in the river
basins of Godavari and Caurverui.
Sol.11 Paraffin wax.
Sol.12 CNG is Compressed Natural Gas.
Sol.13 Petrol and Compressed Natural Gas (CNG)
Sol.14 Food reacts with oxygen in our body and is
broken down into simpler food with the
production of heat. Hence it is regarded as a
fuel for our body.
Sol.15 Kerosene
Sol.16 (a) CNG – Compressed Natural Gas
(b) LPG – Liquefied Petroleum Gas
EXERCISE # 2
Sol.1
Coal and petroleum are formed from the
dead remains of living organisms that is
why they are called fossils fuels.
Sol.2
Coal is hard and is of black in colour.
Sol.3
Coke is used in the extraction of metals and
in the manufacture of steel.
Sol.4
If we use fossil fuels carefully, it will result
in better environment, less risk of global
warming and thdy will be available for
longer period.
(i) 1. LPG (55000 kJ/kg) has higher
calorific value than wood (17000-22000
kJ/kg).
2. LPG does not gives smoke and any
harmful gases but wood gives smoke and
harmful gases like CO on burning.
So LPG is a better domestic fuel than
wood.
(ii) Water is not used to control fires
involving electrical equipment because
water may conduct electricity and harm
those trying to extinguish the fire.
Sol.5
(a) Oil wells are found in Assam and
Bombay high.
Sol.10 (a) CNG – Compressed Natrual Gas. It is
used as a fuel.
(b) The first oil wills were found at Makum
in Assam in 1867.
(b) All liquid fuels are formed from
petroleum.
(a) Coke is formed when coal is heated in
absence of air.
(c) Butane is the main constituent of LPG.
Sol.6
(b) Coke is used :
– as a fuel.
– as a reducing agent in the extraction of
metals.
Sol. 7 Petrol is one of the fractions obtained
during fractional distillation of petroleium.
Petrol, diesel, kerosene and lubricating oil
are four most important products obtained
from petroleum.
Sol.8
A
(i) Petrol
(ii) Liquefied
Petroleum Gas
(iii) Coal
B
Scooter
Cooking
Thermal Power Station
Sol.9
(d) Petroleum is formed by the
sedimentation of dead remains of
microscopic marine plants and animals,
which were buried under the surface of the
earth, millions of years ago.
(e) Green leaves do not catch fire easily
because they contain moisture.
Sol.11 Coal is formed by the slow decay of dead
trees buried under the earth. As the trees
died, they were covered by mud and sand.
This process continued for millions of
years.
Sometimes
earthquakes
and
volcanoes buried entire forests deep inside
the eath. The high temperature and pressure
inside the earth slowly converted the buried
vegetation into coal.